Active protection method and system

ABSTRACT

There is provided an active protection system and an active protection method preferably for airborne platforms. According to the embodiment of the invention, the active protection system is mounted onboard a platform for protecting the platform, and comprises a radar system configured for generating output data including threat output data corresponding to a velocity, a range, and an angle of the threat with respect to the platform in an airspace around the platform, the output data being useful for detecting, identifying and tracking of at least one threat approaching the platform; a countermeasure system capable of launching at least one non-fragmentation interceptor projectile in response to receiving a control command; and a control unit configured for receiving the output data from the radar system and for generating the control command and transmitting the control command to the at least one non-fragmentation interceptor projectile, thereby enabling countering the threat.

FIELD OF THE INVENTION

This invention relates to an active protection method and system andmore specifically to active protection method and system for providingprotection from a threat, particularly for use with a mobile or aerialplatform such as a helicopter, UAV (Unmanned Aerial Vehicle) or thelike.

BACKGROUND OF THE INVENTION

A variety of methods are known relating to protecting a vehicle or thelike from a destructive threat.

For example, U.S. Pat. No. 4,233,605 discloses a Doppler radar signaturesimulator decoy for protecting a helicopter under attack by hostileweapons which home in on a Doppler radar return signal from thehelicopter rotors. The decoy returns a strong radar signal whichduplicates a relatively weaker signal emitted from the helicopterrotors, leading hostile weapons to the decoy.

U.S. Pat. No. 6,980,151 discloses a bi-static continuous wave radarsystem and related methods for detecting incoming threats from ballisticprojectiles includes a remote source of RF illumination, and a localreceiver installed in one or more target aircraft. A first receivingchannel acquires direct path illumination from the source and provides areference signal, and a second receiving channel acquires a scattersignal reflected by a projectile. A processor coupled to each receivercorrects scatter signal Doppler offset induced by relative sourcemotion, isolates narrowband Doppler signals to derive signaturescharacteristic of the projectile, and by executing appropriatealgorithms, compares the derived signatures to modeled signatures storedin memory. If the comparison yields a substantial similarity, theprocessor outputs a warning signal sufficient to initiate defensivecountermeasures.

U.S. Pat. No. 7,066,427 discloses an interceptor device adapted toprotect a platform associated therewith against an incoming threathaving a trajectory by intercepting the threat in an intercept zone.Such an interceptor device comprises a housing defining an axis and acountermeasure device operably engaged with the housing. At least onedetonating charge is housed by the housing and is operably engaged withthe countermeasure device. A controller device is in communication withthe at least one detonating charge, wherein the controller device ishoused by the housing and is configured to direct the at least onedetonating charge to deploy the countermeasure device at least partiallyradially outward with respect to the axis of the housing and incorrespondence with the trajectory of the threat to thereby cause thecountermeasure to impact the threat in the intercept zone.

One active protection defense system is the Flight Guard™ systemavailable by Israel Aircraft Industries™ Ltd. and Elta Systems™ Ltd.,Israel. The Flight Guard™ system is mounted onboard an airborneplatform, and is designed to detect an approaching heat seeking threatand in response, launch a deceiving countermeasure (flares). (The FlightGuard™ system is described e.g. atwww.israeli-weapons.com/weapons/aircraft/systems/flight_guard/Flight_Guard.htm).

Another active protection defense system is the Trophy™ system marketedby General Dynamics™, USA and designed by a consortium comprising RafaelArmament Development Authority Ltd., Israel Aircraft Industries™ Ltd.,Elta Systems™ Ltd and Israel Military Industries™ Ltd., Israel. TheTrophy™ system creates a hemispheric protected zone around the vehiclewhere incoming threats are intercepted and defeated. It has threeelements providing threat detection and tracking, launching andintercept functions. The threat detection and warning subsystem consistsof several sensors, including flat-panel radars, placed at strategiclocations around the protected vehicle, to provide full hemisphericalcoverage. Once an incoming threat is detected, identified and verified,a countermeasure assembly is opened, and a countermeasure device ispositioned in the direction where it can effectively intercept thethreat. Then it is launched automatically into a ballistic trajectory tointercept the incoming threat at a relatively long distance (The Trophy™system is described e.g. at www.defense-update.com/products/t/trophy.htmand www.defensereview.com/modules.php?name=News&file=print&&sid=861).

The following publications are also of interest: U.S. Pat. Nos.7,059,567 and 5,661,254; US Patent application No. 2006/0103569.

RPG's (Rocket Propelled Grenade) represent a serious threat to mobileland and aerial platforms. RPG's are considered the second cause ofdeath of US soldiers in the Iraq war. According to certain assessments,inexperienced RPG operators could engage a stationary target effectivelyfrom 150-300 meters, while experienced users could kill a target at upto 500 meters, and moving targets at 300 meters. One known way ofprotecting a platform against RPG's is to cause explosion or dischargeof the RPG's warhead away from the platform. Another known protectionapproach against RPG's and short range missiles employ fitting theplatform to be protected with armor (e.g. reactive armor, hybrid armoror slat armor).

There is a need in the art for an improved protection system forproviding protection for mobile or aerial platforms, such as ahelicopter or the like, from a projectile threat. There is a need in theart for a protection system for protection against projectile threats,such as RPG's (Rocket Propelled Grenade), short range missiles orrockets and similar threats. There is also a need in the art for aprotection system having relatively very short reaction time. There is afurther need in the art for a protection system for protection againstprojectile threats, being relatively light weighted and suitable to bemounted onboard mobile and aerial platforms.

SUMMARY OF THE INVENTION

Herein, “aerial threat” or “airborne threat” or “threat” are usedinterchangeably to refer to any threat, including projectiles, rockets,missiles and other aerial weapons, having a trajectory and ordnance suchthat may cause damage to a body or location that it is desired toprotect if allowed to intercept and/or detonate and/or impact said bodyor location.

The protection systems and methods of the invention are useful forprotecting many kinds of aerial platforms, including but not limited to,helicopters, UAV's (Unmanned Airborne Vehicle), RPV's (Remotely PilotedVehicle), light aircraft, hovering platforms, low speed travelingplatforms. The protection systems and methods of the invention areuseful for protecting platforms against many kinds of threats, includingbut not limited to, guided missiles or rockets, unguided missiles orrockets, self-guided and maneuvering missile or rocket, heat seekingmissiles or rockets, radar lock missiles or rockets, shoulder missilesor rockets, short range missiles or rockets, RPG (Rocket PropelledGrenade), TOW (Tube-launched, Optically tracked, Wire-guided missile),Hot, Milan, Cornet, Stinger, Strela, and Sager.

The invention can be used with many types and kinds of countermeasureprojectiles, including, but not limited to, non-guided rocket ormissile; guided rocket or missile; and self-guided and maneuveringrocket or missile. According to an aspect of the invention there isprovided an active protection system mountable onboard a platform forprotecting the platform, comprising:

a radar system configured for generating output data including threatoutput data corresponding to a velocity, a range, and an angle of thethreat with respect to the platform in an airspace around the platform,the output data being useful for detecting, identifying and tracking ofat least one threat approaching the platform, and;

a countermeasure system capable of launching at least onenon-fragmentation interceptor projectile in response to receiving acontrol command;

a control unit configured for receiving the output data from the radarsystem and for generating the control command and transmitting thecontrol command to the at least one non-fragmentation interceptorprojectile, thereby enabling countering the threat

According to an embodiment of the invention, the radar system comprisingone or more sensor unit, located at selected locations onboard theplatform. According to another embodiment, the radar system is furtherconfigured for tracking of the at least one projectile, and generatingoutput data corresponding to a velocity, a range and an angle of theprojectile with respect to the platform. According to an embodiment ofthe invention, the radar system is a multibeam radar, a digitalmultibeam radar or a phased-array radar, e.g. a 32-beam multi-beam radarsystem or a digital multi beam radar system. For example, the radarsystem is designed to operate in a 10-20 GHz frequency range, and theweight of the radar system is in the range of 10-100 Kg.

According to an embodiment of the invention, the countermeasure systemcomprises one or more recoilless battery of projectiles, located atselected locations onboard the platform, and associated with at leastone activation unit, the activation unit being operatively connected tothe control unit and configured for responding to a command signal fromthe control unit by launching one or more projectiles. According toanother embodiment of the invention, the countermeasure system comprisesat least one recoilless battery of projectiles, associated with at leastone activation and aiming unit, the activation and aiming unit beingoperatively connected to the control unit and configured for respondingto a command signal from the control unit by aiming and launching one ormore projectiles. Aiming is performed by aiming the battery as a wholeor by aiming at least one part thereof.

According to certain embodiments of the invention, in the case whereguided projectiles are used, the system further comprises a guidancesystem capable of guiding the projectile toward an engagement with thethreat. According to other embodiments of the invention, the systemfurther comprises communication unit operable to facilitate at leastuplink communication with the projectile, thereby enabling guiding theprojectile toward a predicted engagement point with the threat.

According to an embodiment of the invention, the control unit is ahardware/software utility configured for performing the followingoperations:

-   -   (a) detecting, identification and tracking the threat based on        processing of the output data;    -   (b) calculating at least trajectory of the threat and the        platform and determining an engagement point between the threat        and the projectile;    -   (c) determining at least one suitable projectile to be launched,        if at all, and generating fire control command; and    -   (d) repeating any of operations (a) to (c) as many times as        required.

According to another embodiment of the invention, the control unit is ahardware/software utility configured for performing the followingoperations:

-   -   (a) detecting, identification and tracking the threat based on        processing of the output data;    -   (b) calculating at least trajectory of the threat and the        platform and determining an engagement point between the threat        and the projectile;    -   (c) determining at least one suitable projectile to be launched        and, if at all, and generating aiming and fire control command;        and    -   (d) repeating any of operations (a) to (c) as many times as        required.

According to certain embodiments of the invention, the control unit iscommunicatively coupled to platform instrumentation for receiving atleast platform trajectory data and the calculation of the trajectory ofthe threat and the platform is carried out based on platform trajectorydata received from the platform instrumentation. According to otherembodiments, the control unit is further configured for processingplatform trajectory data based on the output data, and the calculationof the trajectory of the threat and the platform is carried out based onthe platform trajectory data. According to other embodiments, thecontrol unit is further configured for tracking the at least oneprojectile, after it was launched, and to perform operations (b) and (c)based on information corresponding to velocity, range and angle of theprojectile with respect to the platform that is measured after launch.According to an embodiment of the invention, in case the countermeasuresystem includes more than one battery of projectiles, each located atdifferent locations onboard the platform, the control unit is furtherconfigured for selecting one from among the batteries, in accordancewith a predefined criteria, for launching the projectile, and fordirecting the command signal accordingly.

According to another aspect of the invention there is provided an activeprotection method for protecting a platform against an approachingthreat, comprising:

-   -   (a) generating radar output data measured by a radar system        mounted onboard the platform, including threat output data        corresponding to a velocity, a range and an angle of the threat        with respect to the platform in an airspace around the platform,        and detecting, identifying and tracking of at least one threat        approaching the platform based on processing of at least the        output data;    -   (b) providing onboard the platform a countermeasure system        capable of launching at least one non-fragmentation interceptor        projectile in response to receiving a control command;    -   (c) based on at least the output data, generating the control        command and transmitting the control command to the at least one        non-fragmentation interceptor projectile,        thereby enabling countering the threat.

According to an embodiment of the invention, the generating of radaroutput data is carried out based on measurements received from one ormore sensor unit, located at selected locations onboard the platform.According to an embodiment of the invention, the method comprisestracking of the at least one projectile, and generating CM output datacorresponding to a velocity, a range and an angle of the projectile withrespect to the platform. According to an embodiment of the invention,the method comprises providing uplink communication with the projectile,thereby enabling guiding the projectile toward a predicted engagementpoint with the threat. According to an embodiment of the invention, themethod comprises: calculating at least trajectory of the threat and theplatform and determining an engagement point between the threat and theprojectile; determining at least one suitable projectile to be launched,if at all; and repeating any one of operations (a) to (g) as many timesas required. According to an embodiment of the invention, the methodcomprises tracking the at least one projectile, after it was launched,and performing the calculating operation and/or determining operationbased on information corresponding to velocity, range and angle of theprojectile with respect to the platform, measured after launch.According to an embodiment of the invention, in case the countermeasuresystem includes more than one battery of projectiles, each located atdifferent locations onboard the platform, the method comprises selectingone from among the batteries, in accordance with a predefined criteria,for launching the projectile, and directing the command signalaccordingly. According to an embodiment of the invention, the methodcomprises receiving platform trajectory data from platforminstrumentation, and the calculation of the trajectory of the threat andthe platform is carried out based on platform trajectory data receivedfrom the platform instrumentation. According to another embodiment ofthe invention, platform trajectory data is processed based on radaroutput data.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 is a schematic representation of an active protection systemaccording to an embodiment of the invention;

FIG. 2 is a more detailed representation of an active protection systemaccording to an embodiment of the invention; and

FIG. 3 is a flow chart illustrating a sequence of operations carried outin accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an active protection system and methodfor protecting a platform against aerial threats. In the following, theconcept of the invention will be disclosed mainly with reference to theprotection of aerial platforms and specifically helicopters (othernon-limiting examples of aerial platforms are RPV (Remotely PilotedVehicle), UAV (Unmanned Airborne Vehicle), light aircraft, hoveringplatforms, low speed traveling platforms and more), however theinvention is not limited thereto. The protection system and method ofthe invention is useful against a variety of threats, such as RPG's,short range guided and unguided missiles or rockets, heat seekermissiles or rockets, radar lock missiles or rockets, shoulder missilesor rockets, and the like.

As illustrated in FIG. 1, a helicopter 100 is fitted with an activeprotection system 10 (not shown in its entirety in FIG. 1), forprotecting the helicopter 100 against one (or a variety of) RPG threat120 (only one threat 120 is shown). According to certain embodiments ofthe invention, the protection system 10 is capable of detecting,identifying and tracking the threat 120, and in response, launchingcountermeasure devices, e.g. one (or a variety of) projectile 41, anddirecting it toward threat 120 (only one such projectile is shown).Projectile 41 may be directed or guided toward a desired engagementpoint EP. According to certain embodiments of the invention, projectile41 is capable of killing threat 120, e.g. by a direct hit or bydischarging the threat (e.g. generating, in proximity to the threat,blast sufficient for harming the threat, such as by discharging of anRPG detonation), substantially without the creation of blast or jet flowthat can harm the platform. According to other embodiments of theinvention, projectile 41 is aimed at absorbing some or all of thekinetic energy carried by the threat. According to certain embodimentsof the invention, the projectile 41 is designed to cause explosion ofthe threat 120 at a certain safety distance R away from the helicopter(by way of non-limiting example, the engagement between the threat andthe projectile is designed to occur at about 30-50 meters away from thehelicopter). Thus, risk of damage of the helicopter, or major partsthereof (e.g. propeller) is minimized or eliminated. Safety distance Ris selected such that the platform will experience no direct hit fromthe threat; its particles (in case the threat exploded) or projectile'sparticles) as well as blast or jet flow. This is different fromsolutions that allow the platform to be protected to absorb a certainamount of energy, by means of a protecting shield or slat armor mountedthereon.

FIG. 2 is a more detailed illustration of a defense system 40 accordingto an embodiment of the invention. As shown, the protection systemincludes a radar system 20, control unit (controller) 30 andcountermeasure system 40.

Countermeasure System

According to an embodiment of the invention, countermeasure system 40comprises at least one battery (or dispenser) of non-fragmentationinterceptor projectiles 41. The battery 40 comprises one or a pluralityof interceptor projectiles 41 such as guided missiles or rockets,comprised in optionally recoilless launch tubes or ejection racks (notshown). According to an embodiment of the invention, the battery 40 maybe placed at a suitable location on the helicopter, and in someembodiments it may be better to have two or more said batteries 40,located at selected locations, for example located on the port side andon the starboard side of the helicopter 100.

Each battery 40 may be associated with an activation unit 42 that isoperatively connected to the controller 30, and is configured forresponding to a command signal from the controller 30 by launching oneor more projectiles 41. For embodiments comprising more than one battery40 at different locations around the helicopter, the controller may alsodetermine which battery is best located to maximize success ofneutralization of the threat, and direct the command signal accordingly.Further, the controller 30 may also determine to launch a projectile 41from a particular battery 40 as opposed to another battery 40 accordingto other criteria, for example when the stocks in another battery may beexhausted, and/or when one battery may be much fuller than another,balancing the weight distribution, so long as there is still enoughsafety margin to destroy the threat safely sufficiently far from thehelicopter. Optionally, the controller 30 may provide a command signalfor more than one projectile 41 to be launched to counter each movingobject 120 of an aerial threat.

Each projectile 41 thus launched can be preprogrammed via the activationunit 42 and with data provided by the controller, to follow a particulardesired trajectory designed to intercept the moving objects at aparticular, preferably safe distance from the helicopter 100.Alternatively, the desired trajectory for projectile 41 may be providedto the projectile (uplink communication) by means of a closed loopguidance system 50, and a corresponding guidance system comprised in theprojectile, enabling the same to be guided to an engagement point viaremote control, using positional and trajectory data thereof providedvia the radar system 20 and controller 30 to correct the trajectory ofthe projectile 41 to the desired trajectory.

According to an embodiment of the invention, the location from which aselected projectile would be launched can be determined as follows: thebatteries are placed at selected locations onboard the platform, e.g. atthe front, back and sides of the platform. During operation, theprojectile best suitable for interception is selected and launched at adirection dictated by the position of the platform at the moment oflaunch. The projectile is directed toward the target (toward thepredicted engagement point) during its flight. According to thisembodiment, the battery and parts thereof cannot be directed toward adirection required for launch or interception, without maneuvering ofthe platform as a whole (e.g. preliminary maneuver performed forpositioning the platform and hence, one of the batteries, in a suitablelaunch position). This embodiment employs guided or self-guided(maneuvering) projectiles. Direction of the projectile toward the threat(toward the engagement point) is carried out via uplink communication(as well as downlink communication, according to certain embodiments ofthe invention), e.g. by providing the projectile with updated threatpositioning data (for example, threat coordinates, engagement pointcoordinates, etc.), or with guidance instructions (for example,appropriate steering signal). It should be understood that the inventionis not limited by the type and kind of guided projectiles and guidancetechnique. According to another embodiment of the invention, thebatteries or parts thereof can be aimed, e.g. moved relative to theplatform, aligned, positioned or directed, prior to launch. According tothis embodiment, the controller (element 30 illustrated in FIG. 2) isfurther configured for determining aiming instructions and generating ofa suitable aiming control signal. According to an embodiment of theinvention (not illustrated in FIG. 2), the countermeasure system(element 40 illustrated in FIG. 2) comprises or is integrated withsuitable aiming means (e.g motorized aiming unit) abapted for aimingAccording to an embodiment of the invention, in order to facilitate veryshort reaction time and interception time, the movement of thebatteries, and/or parts thereof, prior to launch, is measured andconsidered in determining the trajectory of the projectile.

The projectiles 41 are thus configured for accelerating to a high speedand for accurately maneuvering at such speeds to intercept the threat asquickly as possible, and as far away from the helicopter as possible.Further, the projectiles 41 comprise a non-fragmentation warhead thatproduces an explosion having an effective blast radius of about 1 meteror less, that will destroy, discharge or render ineffective any movingobjects of an aerial threat within the blast radius. Furthermore, thecasing of the projectiles 41, in particular of the warhead thereof, maybe made from an ablatable material such as to burn away in the blast,thereby further minimizing any possibility of fragments from thedestruction of the incoming threat to subsequently damage thehelicopter.

Generally, it is preferable to employ light-weighted projectiles (e.g.to load the projectile with minimum amount of detonation required forprotection). This will reduce the overall weight added to the platform,and allow equipping the platform with more projectiles. By way ofnon-limiting example, the interceptor projectiles 41 is a self guidedand maneuvering, light weighted rocket of e.g. about 5 kg or less,carrying e.g. about 1 kg or 0.5 kg of detonation (or less), capable oftraveling about 150-300 meters in a second. The amount of detonationcarried by the projectile is dictated, inter-alia, by the accuracy ofguidance, which in turn, depends, inter alia, upon accuracy of radarreadings.

According to certain embodiments of the invention, countermeasure system40 comprises a combination of projectiles capable of killing threats(e.g. generating blast that activate threat's warhead), and flairscapable of deceiving heat seeker and radar lock threats.

Radar System

According to an embodiment of the invention, radar system 20 comprisesone or more sensors (antenna arrays) 21 (three sensors are shown in FIG.2 by way of a non-limiting example). The sensors are located at selectedlocations onboard the helicopter, thereby providing required coverage.

According to an embodiment of the invention, the radar system isdesigned to perform detection as well as tracking and fire control.Typically, detection radars, e.g. as used in the Flight Guard™ system,are designed as wide angle radars. Typically, tracking radars havenarrower field of view than detection radars. For example, the Trophy™system uses wide angle radar for fire detection and narrow angle radarfor tracking. However, in order to facilitate effective protection, thepresent invention makes use of a single radar system to perform threatdetection and tracking. This could be achieved e.g. by a multi beamradar system, a digital multi beam radar system or a phased array radarsystem. According to an embodiment of the invention, the radar system isa 32-beam multi beam or digital multi beam radar system. According to anembodiment of the invention, the radar system is capable of performingdetection as well as identification, tracking and fire controlfunctions. Having the same radar performing detection, tracking and firecontrol functions contribute to better accuracy and better reactiontime.

As is known to anyone versed in the art, accuracy, efficiency (e.g. invarious weather conditions), antenna size as well as costs depend,inter-alia, on radar operation frequency range. Higher frequencies (e.g.50-60 GHz) typically yield better accuracy and efficiency in bad weatherconditions, require smaller antennas and are substantially expensivesystems compared to lower frequencies. According to an embodiment of theinvention, the radar system is designed to operate in the 10-20 GHzfrequency range, wherein the required accuracy is achieved by means ofsuitable antenna size, radar design and radar data processing.

In order to enable very short reaction time (of about few tens andhundreds of milliseconds from detection up to launch) required forefficient protection from threats like RPG's, the radar system needs tobe highly accurate e.g. providing angular accuracy of about onemilliradian and range accuracy of about 0.5 meter or less. Preferably,the radar system is light weighted, of about 15 kg.

Control Unit (Controller)

For clarification, main processing operations are presented in thefollowing as being carried by a stand-alone control unit 30. It shouldbe understood that the control unit 30 is a hardware/software utilityand as such its functions could be realized by one or more modulesincorporated in the radar system 20; one or more modules incorporated inthe countermeasure system 40; or certain control functions andoperations could be realized by modules incorporated in the radar system20, while others by modules incorporated in the countermeasure system40. Further, such a control unit may be integrated with, or thefunctions thereof provided by, the fire control computer or the missioncomputer of the helicopter 100, when the helicopter is fitted with sucha computer.

According to an embodiment of the invention, the controller 30 isconfigured to perform the following sequence of control operations 300,as illustrated in FIG. 3:

Operation 310—Threat detection, identification and tracking: radar dataregarding airspace around the platform (e.g full airspace hemispherearound the helicopter; half hemisphere above or below the helicopter; orselected zones in the vicinity of the helicopter) is dynamicallyanalyzed. A threat is detected and identified, e.g. based on comparisonof threat signature to a lookout table; comparison of threat velocity toa threshold velocity; analysis of approach direction (angle), range andvelocity; build up of threat trajectory based on data corresponding toseveral measurements, and the like. Trajectory and velocity of theplatform may also be considered, e.g. in order to minimize effect ofreflections from the platform itself.

Upon identification, the threat is tracked, and output data, includingthreat output data corresponding to velocity, range and an angle of thethreat with respect to the platform, is dynamically generated.

Operation 320—trajectory calculations and determination of engagementpoint: In accordance with operational requirements, the desiredengagement point (point EP illustrated in FIG. 1) is determined, basedon calculation and prediction of threat and projectile trajectories.

According to an embodiment of the invention, the engagement point isdetermined such that neutralization of the threat may occur at a safedistance away from the helicopter (distance R illustrated in FIG. 1).According to another embodiment of the invention, the engagement pointis selected such that direct hit of the threat by the projectile isexpected. According to yet another embodiment of the invention, bestsuitable for protection against RPG's, the engagement point isdetermined such that blast generated by explosion of the projectile'swarhead will most probably discharge the threat's warhead before itreaches the platform.

According to an embodiment of the invention, operation 320 includescalculation, for each moving object whether it is expected to interceptand collide with the helicopter 100 or not, at the predicted flight pathof the helicopter 100. The moving objects which are determined to have atrajectory relative to the helicopter 100 that does not present a threatthereto, and will fly at a safe enough distance that even if itdetonates no damage may be expected to the helicopter, may optionally beignored, or optionally destroyed. However, for each of the movingobjects which are considered to pose a threat to the helicopter, forexample calculated to pass sufficiently close to the helicopter tocollide with it or such that a detonation of a warhead carried therebymay cause damage to the helicopter, a command signal is generated andtransmitted to the battery 40 for launching one or more interceptorprojectiles 41 to counter the threat.

Operation 330—CM (countermeasure) analysis and generation of a firecontrol command: Upon identification of the threat and the determinationof a suitable engagement point, a suitable countermeasure device is alsodetermined. In accordance with various embodiments of the invention, byway of non-limiting example only, the following control parameters areconsidered in order to determined the suitable CM device: time oflaunch; direction of launch; selection of battery from which theprojectile is to be launched; selection of a specific projectile from aspecific battery to be launched; determination of number and order ofprojectiles to be launched; explosion time of projectile's warhead;updated guidance information.

According to one embodiment of the invention, a result of an approachanalysis, e.g. identifying a threat approaching the platform (as opposedto detection of a non-approaching threat in the vicinity of theplatform) will dictate the reaction of the protection system. Threenon-limiting examples of the above are: (i) in response to approachdetection and above a predefined threshold closing velocity and/or rangeand/or direction, a projectile will be launched from the platformwithout performance of preliminary platform maneuver; (ii) in formationflight, each platform conduct approach analysis that includesidentification of approach toward the platform as well as toward theformation, based upon the platform role in the formation; and (iii) inresponse to approach detection and above a predefined threshold closingvelocity and/or range and/or direction, a projectile will be launchedfrom the platform even in a case where not enough radar data is measuredin order to determined the engagement point and guidance data, prior tolaunch.

According to certain embodiments of the invention, by way of anon-limiting example only, and in order to comply with certainoperational requirements and constraines, alternative or additionalcontrol parameters are considered, as follows: height of flight;formation flight details; terrain details; mission details and the like.

It should be understood that various operational scenarios could beaddressed by the protection system, without departing from the scope ofthe present invention. By way of a non-limiting example, suchoperational scenarios may encompass the following: detection andidentification of a threat without launch of a countermeasure projectile(e.g. when such a launch may endanger other platforms or humansoperating in the vicinity of the threatened platform; in formationflight, launch of a countermeasure projectile to intercept a threatendangering neighboring platform; in a networked environment, receivingalert of a threat and/or fire control command (including guidanceinformation) from an external source (e.g. protection system mountedonboard another platform which is a member of the same network).

According to one embodiment of the invention, the controller 30 may beadapted for operation when the helicopter is flying in proximity toother friendly aircraft including other helicopters, for example. Suchproximity flying may include formation flying, for example. In suchcases, the control unit 30 may be further adapted to identify whetherother flying objects, e.g. as picked up by the helicopter radar, inparticular radar system 20, and/or by using position information sharedbetween friendly members of a communication network, are friendlyaircraft. Having positively identified one or more friendly aircraft,the operation of the system 10 may be modified as follows. First, thecontroller 30 generates location and trajectory data for each friendlyaircraft from data provided by the radar system 20, in a similar mannerto that described with respect to an aerial threat, mutatis mutandis.Then, the controller determines whether the interception trajectoriesfor the projectiles 41, and their blast radius when neutralizing theaerial threat, would endanger the friendly aircraft, at their projectedpositions. If the determination is that no danger is posed, then theprojectiles are launched as before. On the other hand, if the projectiletrajectories, or their blast radius could cause damage, then a differentcourse of action is taken, e.g. in the case of a UAV operating inproximity to other platforms or forces, a decision to sacrifice thethreatened UAV in order to save the other forces or platforms, could betaken

Operation 340—transmitting control command to the countermeasure system:According to one embodiment of the invention, the projectile ispreprogrammed with flight directions prior to launch. According toanother embodiment of the invention, best suitable for protectionagainst fast approaching threats, the projectile is a guided rocket andguidance information is dynamically calculated and transmitted to theprojectile (uplink communication). According to another embodiment ofthe invention, the control command includes aiming instructions thatwill be carried out by a suitable aiming unit, for aiming the batteryitself or parts thereof.

In order to facilitate launch and guidance of more than one projectile(parallel operation), each projectile is assigned (e.g. by thecontroller, the radar or the battery) with an identity, and thisidentity is used (e.g. by the controller, radar, guidance system) forgenerating the appropriate guidance updates. The identity of theprojectile is also used for communicating with the projectile. Accordingto an embodiment of the invention, each projectile is assigned with anidentity prior to launch. Upon launch the identity is used by allcomponents of the active protection system in all processing operationsrelating to the same projectile. The guidance information that isgenerated by the guidance system is respectively assigned with theidentities of the projectiles that were launched, and each projectile isresponsive to the guidance information that is assigned to its ownidentity.

In order to simplify explanations, the operations carried out by thecontrol unit were presented as discrete operations, carried out in asequential manner. It should be understood that the above detailedcontrol operations are carried out rapidly, in a dynamic and iterativemanner. For example, the determination of the engagement point is doneiteratively based on newly measured radar data, and updated guidanceinformation is generated and transmitted to the projectile in a dynamicmanner. In order to achieve very short reaction time and interceptiontime, the control unit as well as the radar system, are adapted for highupdate rate, in order to provide the projectile with rapid and accurateguidance updates, needed to intercept the target e.g. at 30-50 metersaway from the helicopter in about 300 milliseconds.

The concept of the invention was described mainly with reference to asimplified scenario, where only one projectile is launched against onlya single threat. It should be understood that where the aerial threatcomprises more than one moving object, the trajectory of each object isseparately determined and tracked in parallel. The same applies to thecase where more than one projectile is launched against a threat. Thus,each of the above detailed operations 310-340 is repeated as many timesas required.

In the above description, it is assumed that the protection system isintegrated or designed to interface with platform systems andinstrumentation, such that information collected by these systems isavailable to the protection system. For example, platform data (e.g.speed, direction of flight, attitude, altitude and so on) is externallyprovided to the protection system. It should be understood that theprotection system may include additional elements to those describedabove with reference to FIG. 2, in order to autonomously acquire allnecessary information.

The aforesaid reaction time of the system 10 may be defined as theminimum elapsed time required by the system 10 to identify a threat,calculate an interception trajectory for a projectile 41 based on thetrajectory of the threat and of the helicopter, and launch at least onemissile so that it destroys or neutralize the threat at a sufficientlyspaced distance from the helicopter such that the blast, and possibledebris created thereby, will not damage the helicopter. Such a reactiontime may be, for certain operational needs, for example from a fewmilliseconds, tens and hundreds of milliseconds up to a few seconds, asthe operational requirements dictate, and the blast may be required tobe more than 30 meters away from the helicopter 100.

As described before, in order to provide such a short reaction time, theprotection system is designed with a highly accurate, wide anglemulti-beam or phased-array radar system capable of detection,identification, tracking and fire control. The radar system is designedwith several sensors located on different locations onboard theplatform. Thus, the radar is capable of providing very accurate outputdata in a relatively very short time. Furthermore, the countermeasuresystem preferably is designed to have several batteries of projectileslocated at different locations onboard the platform, thus enablingselecting the suitable countermeasure projectile which provides maximumkill success. Good reaction time is also achieved due to the efficientcontrol processing schemes, e,g, as described above with reference toFIG. 3. Good reaction time is achieved by aiming the projectilebattery—or parts thereof—prior to launce. The use of guided orself-guided (maneuvering) projectiles together with efficient guidanceprocessing further reduce reaction time.

In embodiments of the present invention, the radar system 20 is criticalto the effectiveness of the protection system 10, and the operationparameters of the radar system are defined, at least in part, by thetype of threat and a minimum safety distance R away from the helicopter100 at which the threat 120 can be intercepted. The engagement distanceR may be determined from a variety of factors such as, for example, thesensitivity of the radar system 20, the time necessary to actuate thecountermeasure system 40 to launch the projectile 41, the effectiveness,accuracy acceleration and speed of the projectile 41, and the nature ofthe platform 100 to be protected.

While the invention has been described in the context of an airbornevehicle such as a helicopter, the system 10 may be configured foroperation with any other suitable aircraft, including small or large,manned or unmanned, fixed wing or rotor aircraft, or balloons or othertypes of air vehicles.

The system 10 may be configured for operation at a location for theprotection thereof, for example a building, communication or radarinstallation, a camp, and so on, in a similar manner to that describedabove, mutatis mutandis, with the optional difference that weightconstraints may be even more relaxed than in the case of movingvehicles, and furthermore, the radar system 20, controller 30 andbatteries may optionally be significantly distanced one from another.For example, a central radar system may be provided in a camp, while atthe same time providing a plurality of batteries at the periphery of thecamp.

1-40. (canceled)
 41. An active protection system mountable onboard anaerial platform for protecting the aerial platform, the protectionsystem comprising: a multi-beam or phased array radar system configuredfor generating output data including threat output data corresponding toa velocity, a range, and an angle of a threat with respect to the aerialplatform in an airspace around the platform, said output data beinguseful for detecting, identifying and tracking of at least one threatapproaching the platform, said radar system enabling reduced weight ofthe protection system, and a reduced response time of the protectionsystem; a countermeasure system comprising a plurality of projectilesand being capable of launching at least one projectile in response toreceiving a control command; and a control unit configured and operablefor receiving and analyzing said output data from said radar system, tothereby detect, identify and track said at least one threat approachingthe platform; determining a desired engagement point for said at leastone threat; and utilizing said determined desired engagement point forgenerating the control command indicative of selection of one or moreprojectiles from said plurality of projectiles suitable for interceptingsaid threat at said engagement point and transmitting said controlcommand to said countermeasure system, thereby enabling countering saidthreat.
 42. A system according to claim 41, wherein the selectedprojectile is suitable for engagement with said threat at saidengagement point by at least one of a type of the projectile and itslocation within the platform.
 43. A system according to claim 41,wherein said platform is one of the following platforms: helicopter, UAV(Unmanned Airborne Vehicle), RPV (Remotely Piloted Vehicle), lightaircraft, hovering platform, low speed traveling platform.
 44. A systemaccording to claim 41, wherein said threat is one of the followingthreats: non-guided missile or rocket; guided missile or rocket;self-guided and maneuvering missile or rocket; heat seeking missile orrocket; radar lock missile or rocket; laser guided missile or rocket;short range missile or rocket; shoulder missile or rocket; RPG (RocketPropelled Grenade); TOW (Tube-launched, Optically tracked, Wire-guidedmissile); Hot; Milan; Cornet; Stinger; Strela; and Sager.
 45. A systemaccording to claim 41, wherein said projectile is one of the following:non-guided rocket or missile; guided rocket or missile; and self-guidedand maneuvering rocket or missile.
 46. A system according to claim 41,wherein said multi-beam or phased array radar system comprises one ormore sensor units, located at selected locations onboard the platform.47. A system according to claim 41, wherein said radar system is furtherconfigured for tracking of said at least one projectile, and generatingoutput data corresponding to a velocity, a range and an angle of theprojectile with respect to the platform.
 48. A system according to claim41 wherein said multibeam radar system comprises a digital multibeamradar.
 49. A system according to claim 48 wherein the radar system is a32-beam multi-beam radar system.
 50. A system according to claim 49wherein the radar system is designed to operate in a 10-20 GHz frequencyrange.
 51. A system according to claim 41, wherein weight of said radarsystem is in the range of 10-100 Kg.
 52. A system according to claim 41,wherein said countermeasure system comprises one or more recoillessbattery of the projectiles, located at selected locations onboard theplatform, and is associated with at least one activation unit, theactivation unit being operatively connected to the control unit andconfigured for responding to a command signal from the control unit bylaunching one or more projectiles.
 53. A system according to claim 41,wherein said countermeasure system comprises at least one recoillessbattery of the projectiles, associated with at least one activation andaiming unit, the activation and aiming unit being operatively connectedto the control unit and configured for responding to a command signalfrom the control unit by aiming and launching one or more projectiles.54. A system according to claim 53 wherein said aiming is performed byaiming the battery as a whole or by aiming at least one part thereof.55. A system according to claim 41, wherein said countermeasure systemis further capable of launching flairs and/or chaffs.
 56. A systemaccording to claim 41, further comprising a guidance system capable ofguiding the projectile toward an engagement with the threat.
 57. Asystem according to claim 41, further comprising communication unitoperable to facilitate at least uplink communication with theprojectile, thereby enabling guiding the projectile toward a predictedengagement point with the threat.
 58. A system according to claim 41,wherein said control unit is a hardware/software utility configured forperforming the following operations: (a) detecting, identification andtracking the threat based on processing of said output data from theradar system; (b) calculating at least trajectory of the threat and theplatform and determining the engagement point for the detected threatwith respect to the platform; (c) determining said at least one suitableprojectile to be launched, if at all, and generating the control commandcomprising a fire control command; and (d) repeating any of operations(a) to (c) as many times as required.
 59. The system according to claim58, wherein said control command generated by the control unit comprisesan aiming and fire control command.
 60. A system according to claim 58,wherein said control unit is communicatively coupled to platforminstrumentation for receiving at least platform trajectory data and saidcalculating is carried out based on platform trajectory data receivedfrom said platform instrumentation.
 61. A system according to claim 58,wherein said control unit is further configured for processing platformtrajectory data based on said output data, and said calculating iscarried out based on said platform trajectory data.
 62. A systemaccording to claim 58, wherein said transmitting said control command tosaid countermeasure system is carried out prior to launch.
 63. A systemaccording to claim 58, wherein said transmitting said control command tosaid countermeasure system is carried out in a dynamic manner prior tolaunch and afterwards.
 64. A system according to claim 41, wherein saidplurality of projectiles comprises substantially non-fragmentation typeprojectiles.
 65. A system according to claim 58, wherein said controlunit is further configured for tracking said at least one projectile,after it was launched, and to perform operations (b) and (c) based oninformation corresponding to velocity, range and angle of the projectilewith respect to the platform that is measured after launch.
 66. A systemaccording to claim 41, wherein said countermeasure system comprises oneor more battery of the projectiles, each located at different locationsonboard the platform, the control unit being configured and operable forselecting one from among said batteries, in accordance with a predefinedcriteria, for launching the projectile, and directing the command signalaccordingly.
 67. An active protection method for protecting an aerialplatform against an approaching threat, the protection methodcomprising: (a) generating radar output data measured by a multi beam orphased array radar system mounted onboard the aerial platform, theoutput data including threat output data corresponding to a velocity, arange and an angle of the threat with respect to the aerial platform inan airspace around the platform, and detecting, identifying and trackingof at least one threat approaching the platform based on processing ofat least said output data, thereby providing a reduced response time ofthe protection system; (b) providing onboard the platform acountermeasure system comprising a plurality of projectiles and beingcapable of launching at least one projectile in response to receiving acontrol command; (c) receiving and analyzing said output data, anddetecting, identifying and tracking said at least one threat approachingthe platform; (d) determining a desired engagement point for said atleast one threat; (e) utilizing said determined desired engagement pointfor generating said control command, indicative of selection of one ormore projectiles from said plurality of projectiles suitable forintercepting said threat at said engagement point; and, (f) transmittingsaid control command to said countermeasure system thereby enablingcountering said threat.
 68. A method according to claim 67, wherein theselected projectiles are suitable for engagement with said threat atsaid engagement said engagement point by at least one of a type of theprojectile and its location within the platform.
 69. A method accordingto claim 67, wherein said platform is one of the following platforms:helicopter, UAV (Unmanned Airborne Vehicle), RPV (Remotely PilotedVehicle), light aircraft, hovering platform, low speed travelingplatform.
 70. A method according to claim 67, wherein said threat is oneof the following threats: non-guided missile or rocket; guided missileor rocket; self-guided and maneuvering missile or rocket; heat seekingmissile or rocket; radar lock missile or rocket; laser guided missile orrocket; short range missile or rocket; shoulder missile or rocket; RPG(Rocket Propelled Grenade); TOW (Tube-launched, Optically tracked,Wire-guided missile); Hot; Milan; Cornet; Stinger; Strela; and Sager.71. A method according to claim 67, wherein said generating radar outputdata is carried out based on measurements received from one or moresensor unit, located at selected locations onboard the platform.
 72. Amethod according to claim 67, further comprising: (g) tracking of saidat least one projectile, and generating countermeasure output datacorresponding to a velocity, a range and an angle of the projectile withrespect to the platform.
 73. A method according to claim 67, furthercomprising: (h) providing uplink communication with the projectile,thereby enabling guiding the projectile toward a predicted engagementpoint with the threat.
 74. A method according to claim 67, furthercomprising: (i) calculating at least trajectory of the threat and theplatform and determining the engagement point for the detected threatwith respect to the platform; (j) determining said at least one suitableprojectile to be launched, if at all; (k) repeating any one ofoperations (a) to (g) as many times as required.
 75. A method accordingto claim 67, wherein said transmitting said control command to saidcountermeasure system is carried out prior to launch.
 76. A methodaccording to claim 67, wherein said transmitting said control command tosaid countermeasure system is carried out in a dynamic manner prior tolaunch and afterwards.
 77. A method according to claim 74, furthercomprising tracking said at least one projectile, after it was launched,and performing said calculating operation and/or determining operationbased on information corresponding to velocity, range and angle of theprojectile with respect to the platform, measured after launch.
 78. Amethod according to claim 74, wherein the countermeasure systemcomprises one or more battery of the projectiles each located atdifferent locations onboard the platform, operation (j) furthercomprising: selecting one from among said batteries, in accordance witha predefined criteria, for launching the projectile, and directing thecommand signal accordingly.
 79. A method according to claim 67, furthercomprising: (l) receiving platform trajectory data from platforminstrumentation; and wherein said calculating is carried out based onplatform trajectory data received from said platform instrumentation.80. A method according to claim 67, further comprising: (i) processingplatform trajectory data based on said output data; and wherein saidcalculating is carried out based on said platform trajectory data.